生物胺降解菌Staphylococcus xylosus JCM 2418的特性研究及应用

从鱼露中筛选获得一株具有生物胺降解能力的木糖葡萄球菌——Staphylococcus xylosus JCM 2418,对其安全性、发酵性能进行评价同时对生物胺降解相关酶展开分析,并将其接种至发酵食品中进行应用,监测发酵食品生物胺降解率以及风味的变化情况。结果表明,S.xylosus JCM 2418表现出弱耐药性,不具有溶血性,不产生生物膜;具有良好的耐盐性、蛋白酶和脂肪酶活性;生物胺降解相关酶为细胞膜上的胺氧化酶;应用在发酵食品中,可以有效控制生物胺的积累,同时改善发酵产品的风味,为提升发酵产品品质提供优良菌种。

Staphylococcus xylosus Isolation of Conjunctival Secretions in an 8-Year-Old Child at Sikasso Hospital (Mali): About a Case

Staphylococcus xylosus is a species of bacteria belonging to the genus Staphylococcus. This genus currently includes several species and subspecies. We distinguish between 2 groups: the group of coagulase-positive staphylococci (CoPS) and coagulase-negative staphylococci (CoNS), a larger group that includes more than forty species and subspecies. Among the CoNS, Staphylococcus xylosus occupies a special place because it is frequently isolated from meats, dairy products, and agricultural environments. It is commonly used in fermentation due to its primary role in the flavor and color development of fermented products. It is a commensal bacterium of the skin of small mammals and farm animals, where it constitutes the majority of flora. In this species, there are a large number of strains, including phenotypes and genotypes. Although S. xylosus is actually a recognized non-pathogenic species, a few strains can be potentially dangerous. They can thus be responsible for mastitis and dermatitis in cattle. With the multiplicity of breeding farms, the consumption of livestock products and the increasingly frequent contact of humans with animals a few rare cases of human opportunistic infections have also been reported in the literature. These include pyelonephritis, endocarditis, urinary, lymphatic, and lymph node infections, contamination of orthopedic materials and catheters. Thereby, we report the case of a lingering and chronic infection of the lacrimal tract by Staphylococcus xylosus in an 8-year-old child in the Ophthalmology Department of Sikasso hospital in Mali.

Sucrose enhances the chromogenic ability of Staphylococcus xylosus by improving nitric oxide synthase activity

In this paper,the effect of different concentrations of sucrose stress on color formation of the Staphylococcus xylosus was investigated.The results showed that the highest a*value and the best coloring effect similar to those of nitrite were observed after the addition of 0.05 g/mL sucrose to stress the S.xylosus.UV-Vis and electron spin resonance spectra analysis showed that production of coloring product Mb-NO was significantly enhanced after 0.05 g/mL sucrose stress.The growth curve,reactive oxygen content,cell cycle,nitric oxide synthase(NOS)activity,zeta potential,cell size,and protein composition of S.xylosus were investigated to reveal the mechanism of sucrose stress to enhance the coloring effect of the strain.The result showed that sucrose inhibited the growth of S.xylosus,which changed the physiological state by activating the oxidative stress response.The stress altered the rate of intracellular metabolism of S.xylosus by delaying the cell cycle and increasing cell surface zeta potential and cell particle size.These changes altered the protein composition of the cells and significantly enhanced the activity of intracellular NOS,which could improve the chromogenic ability of S.xylosus.This study will provide theoretical support for sucrose stress on S.xylosus to enhance its coloring effect,and sucrose stress for S.xylosus might be a promising biological alternative to nitrite in meat products.

Effect of proteolytic starter culture isolated from Chinese Dong fermented pork(Nanx Wudl)on microbiological,biochemical and organoleptic attributes in dry fermented sausages

The effect of a proteolytic starter culture isolated from Nanx Wudl,on microbiological,biochemical and organoleptic attributes of dry fermented sausages was investigated during processing.Based on preliminary screening,the combination of Staphylococcus xylosus SX16 and Lactobacillus plantarum CMRC6,showing excellent proteolytic activity in vitro,was selected as the multi-strain starter(starter LS).For comparison,the single-strain starter culture of L.plantarum CMRC6(starter LB)and non-inoculated control were also tested.During fermentation,lactic acid bacteria and staphylococci dominated the microbiota and suppressed the Enterobacteriaceae growth in LS-inoculated sausages.The addition of LS starter accelerated acidification and proteolysis during ripening,improving the contents of total free amino acids and several essential free amino acids(Phe,Ile and Leu).Volatile compounds analysis revealed that LS-fermented sausage showed the highest abundance of 3-methyl-1-butanol,probably due to the inoculated S.xylosus.The inoculation of LS starter improved the sensory properties of sausages,especially the flavor attribute.Therefore,S.xylosus SX16 and L.plantarum CMRC6 are promising candidates for inclusion as multi-strain starters in the manufacture of gourmet fermented dry sausage.